From: | Bruce Momjian <pgman(at)candle(dot)pha(dot)pa(dot)us> |
---|---|
To: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
Cc: | John Brothers <johnbr(at)mindspring(dot)com>, pgsql-general(at)hub(dot)org, pgsql-sql(at)hub(dot)org |
Subject: | Re: [SQL] RE: [GENERAL] Problem with SELECT on large negative INT4 |
Date: | 2000-01-28 05:31:26 |
Message-ID: | 200001280531.AAA11561@candle.pha.pa.us |
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Lists: | pgsql-general pgsql-hackers pgsql-sql |
> Actually, if Nicolas' table contains both very large positive and very
> large negative integers, then his index could be messed up pretty badly.
> What Hiroshi saw (and I missed :-() was that btint4cmp can fail and
> return a result of the wrong sign if the difference between two integers
> overflows. Since index sorting depends critically on the assumption
> that the comparator always returns consistent results (a < b and b < c
> must imply a < c, but this can fail if a - c overflows), you could have
> an out-of-order index. And then probes into the index could fail to
> find items they should find ... which is exactly the complained-of
> symptom.
>
> Hiroshi neglected to mention that you'd probably need to drop and
> recreate the index after applying the patch; if it's indeed out of
> order, just patching the comparator bug isn't enough to fix it.
>
Does Hiroshi's patch get applied?
--
Bruce Momjian | http://www.op.net/~candle
pgman(at)candle(dot)pha(dot)pa(dot)us | (610) 853-3000
+ If your life is a hard drive, | 830 Blythe Avenue
+ Christ can be your backup. | Drexel Hill, Pennsylvania 19026
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